1. Field of the Invention
The present invention relates to a perforator for making perforations along at least one lateral side of a continuous strip of photographic film, or the like, within a limited longitudinal section thereof.
2. Description of the Related Art
Conventional 35 mm, or 135-type, photographic film (ISO 135: 1979) has perforations formed at constant intervals along the entire length thereof, for example, as shown in FIG. 25. Perforators for making such continuous perforations 10 are disclosed in JPA 61-214999 and JPU 4-2800, for example.
Known perforators have a measuring feeder for feeding the continuous film by a given length into a die set mechanism. The die set mechanism sandwiches the fed portion of the continuous film to die-punch the same and thus simultaneously form a predetermined number of perforations in the film. The perforations are equally spaced in the film feeding or transporting direction. The measuring feeder and the die set mechanism are synchronously driven by a common drive source through respective drive systems. At least one of these drive systems is coupled to the drive source through a cam index mechanism. Thereby, the interval of die-punching of the die set mechanism is controlled to be constant, and the measuring feeder feeds the continuous film by a length corresponding to the predetermined number of perforations. In this way, the equally spaced perforations 10 are formed in continuous succession. Thereafter, the continuous film 11 is cut into individual filmstrips 13 as shown by phantom lines in FIG. 25. Picture frames are exposed or recorded in proper locations 12 by advancing the filmstrip 13 by one-frame amount after each exposure in a camera. The perforations 10 have mainly been utilized for such a one-frame film advancement.
Recently, a photographic filmstrip has been disclosed, for example, in JPA 4-96056, that has one perforation for each frame exposure location along one or both lateral sides thereof. For example, as shown in FIG. 26, a perforation 14 is disposed on each lateral side of each frame exposure location 12 of an individual filmstrip 15. This type photographic filmstrip is mainly directed for use in a film cassette having a film leader advancing function, in which a film leader of the filmstrip entirely located within the cassette can be advanced to the outside of the cassette by rotating a spool of the cassette. Such a film cassette is disclosed, for example, in U.S. Pat. No. 4,846,418. Therefore, a camera for use with this type film cassette does not need a conventional film advancing sprocket, and instead, adopts an optical sensor for detecting the perforations 14 to determine and position the frame exposure location 12 in an exposure opening of the camera.
For this reason, the perforations 14 are merely formed in a longitudinal section extending from the first to the last frame exposure location 12 of each filmstrip 15. This section will be hereinafter referred to as effective frame recording section 1 or simply section 1. A section which does not have frame exposure locations 12 and hence does not have frame positioning perforations 14 will be referred to as ineffective frame recording section 2 or simply section 2, as indicated in FIG. 26.
The perforations 14 of the above-described new arrangement cannot be made by the above-described conventional perforator. This is because the measuring feeder and the die set mechanism are synchronously driven by the same drive source, so that it is impossible to change the drive pattern of the measuring feeder or the die set mechanism independently from one another to thereby allow a position of the film to be advanced without perforation.
Conventional 110-type photographic filmstrips also have perforations which are disposed one for each frame exposure location, and are therefore disposed merely within effective recording sections. A perforator for the 110-type filmstrip conventionally uses a die set mechanism having punches and dies of a number corresponding to a predetermined frame number of the individual filmstrip. All the perforations of the predetermined number are thus provided simultaneously by a die-punching stroke of the die set.
However, there are usually several variations in the number of picture frames available on one filmstrip. Therefore, the above-described 110-type perforator needs to prepare several kinds of die sets in order to correspond to the frame number variation of the filmstrips to be manufactured. The cost of the die sets is substantial. Also, it is necessary to interrupt running the perforator so as to interchange the die set mechanisms each time the frame member format is changed. This results is lowering the efficiency of the perforator.